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Yonsei UniversityOptoelectronics (16/2)
High-Speed Circuits & Systems Lab.Dept. of Electrical and Electronic Engineering
Yonsei University
Waveguide and DirectionalCoupler
MODE Simulation
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Lumerical Solutions3D Maxwell solver(FDTD)
Modal analysis(MODE)
Charge transport & heat transfer(DEVICE)
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Lumerical MODE Solution• FDE(Finite Difference Eigenmode) solver
-Calculate physical properties of waveguide modes-Solve Maxwell’s equations for cross-sectional mesh
• 2.5D varFDTD(Finite Difference Time Domain)-Time domain simulation with approximation-2D simulation speed with 3D accuracy
• EME(Eigenmode Expansion) solver-Frequency domain simulation
Most simulations will be held with these solvers
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
MODE Window
Script File Editor
Command Window
3D Structure Viewer
Structure Setting
Simulation Setting Simulation
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Waveguide Structure• Drawing structure
– Example) Make strip waveguide– Height: 220 nm– Width: 500 nm– Length: 30 μm– Core material: Si– Cladding material: SiO2
500nm
220nm
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Structure Build(GUI)• Cladding
You can use both (x & span) or (x min & max) for setup
Mesh order: If materifolded, choose materwhich has smaller meorder
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Simulation Setup(GUI)• Eigenmode Solver
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
MODE Solutions
Calculatedmodes
Infers whether the mode is true or notfrom effective index
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Group Index(ng)
①
②
③
④Change to group index
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Sweep WidthSweep waveguide width from 100nm to 300nm with 50nm step
To verify single mode condition
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Sweep Results
SiO2 refractive index: 1.44
Single modecondition
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Design Exercise 2-1What is the single-mode condition for the given thickness of rib waveguide? Also, calculate group index(ng) for the single-mode rib waveguide.
-220nm thick & 100nm slab at 1550nm
Due: 27 Nov. in class
100nm
Width
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Tips for Design Exercise 2-1• Condition for guidance of rib waveguide
:neff_total>neff1:Making same environment as strip waveguide
• How to get neff1:Use 1-D Z:X prop simulation in FDE solver
neff1 neff1
Calculateeffective index here
Optoelectronics (17/2)Optoelectronics (17/2)
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Waveguide coupler• Y-branch coupler
• Ideally 50:50 power splitter• Bezier Curve• Curve shape change due to x2, y2
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Y-branch coupler• Waveguide structure group
Put waveguide structure value in here
Change the shape of curve• Download y_splitter.lms file at YSCEC
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Simulation Setup• 2.5D FDTD Solver Setting(Variational FDTD Solver)
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Simulation Setup• Source Setting
(MODE source)
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Simulation Setup• Monitor 1 Setting (Frequency domain field and power)
-Frequency point should be large enough
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Simulation Setup• Monitor 2 Setting (Frequency domain field and power)
-Frequency point should be large enough
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Run Simulation• After setup, run simulation
Yonsei UniversityOptoelectronics (16/2)Optoelectronics (17/2)
Result• Monitor 1 (Right click) Visualize T• Monitor 2 (Right click) add to visualizer 1 T
50:50 power splitting for each wavelength